This study is designed to compare and quantitate the components of myocardial work during dynamic exercise (EST) and Dobutamine Stress Testing (DSE). This will facilitate a better understanding of cardiac physiology during high-dose dobutamine infusion and its relationship to maximal dynamic exercise. We aim to define the association between measured myocardial oxygen consumption (MVO2) with non-invasive indices during dobutamine infusion compared to dynamic exercise. Methods: Twenty subjects (reflecting the population evaluated by EST and DSE at University of Texas Medical Branch) will perform bicycle exercise test followed by a DSE during invasive hemodynamic monitoring. Heart rate, blood pressure, electrocardiogram, echocardiogram, intracardiac pressures, oxygen saturation, cardiac output and coronary sinus flow will be measured. Wall stress and MVO2 will be calculated. Conclusions: An improved understanding of the physiology may facilitate changing DSE from being primarily a diagnostic test to one that has significant prognostic value. A direct comparison to exercise testing may accomplish this goal. This should provide insight into the optimal use of DSE.